Generally, the handles of car doors are used for opening or closing the doors. The lights of cars are installed at the front or rear sides of the cars and thus the alert effect is limited at the front and rear sides. No alert is provided at the lateral sides of the cars. Therefore, for the people or cars at the lateral sides, no alert is provided and they can not keep attention to the movement of the cars. Thus, they feel danger in driving. As a result, there is an eager demand for resolving this problem.